Extruder height toggling

ABSTRACT

A multi-extruder includes a passive height control mechanism that adjusts the relative height of its extruders without the use of additional, active components. Further, the height control mechanism may employ ramped control surfaces that mitigate noise and vibration by gradually transferring vertical loads while transferring from one active extruder to another.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/570,468 filed on Sep. 13, 2019, which claims priority to U.S.Provisional Application No. 62/731,551 filed on Sep. 14, 2018 and U.S.Provisional Application No. 62/777,587 filed on Dec. 10, 2018, where theentire contents of each of the foregoing applications are herebyincorporated by reference.

FIELD

The present disclosure relates generally to three-dimensional printing,and more specifically to a toggling height control system for amulti-extruder assembly.

BACKGROUND

Multi-extruder assemblies typically employ some type of height controlmechanism so that an inactive extruder can be raised (or an activeextruder lowered, or both) to avoid disturbing a layer of materialdeposited by its active extruder counterpart. However, switching betweendifferent extruders in this context can be cumbersome, and may requireadditional hardware, control complexities, and so forth. Moreover, thephysical height adjustment can generate significant noise and vibrationsthat may damage printer components or create unwanted background noiseduring a print. There remains a need for a multi-extruder printer withimproved height control.

SUMMARY

A multi-extruder includes a passive height control mechanism thatadjusts the relative height of its extruders without the use ofadditional, active components. Further, the height control mechanism mayemploy ramped control surfaces that mitigate noise and vibration bygradually transferring vertical loads while transferring from one activeextruder to another.

In one aspect, an extruder assembly disclosed herein includes a firstextruder including a first follower, the first extruder defining a firstextrusion path, and at least one portion of the first extrusion pathdefining a z-axis. The extruder assembly also includes a cam having aworking surface movable relative to the first extruder and shaped totranslate a first movement of the cam along an x-axis or a y-axis into asecond movement of the first follower along the z-axis, the firstfollower movable along the working surface of the cam as the workingsurface moves relative to the first extruder to raise the first followeralong the z-axis. The extruder assembly also includes a supportengageable with the cam to reverse the first movement of the cam andlower the working surface adjacent to the first follower along thez-axis, and a damper coupled to the support, the damper engageable withthe first extruder to receive a z-axis load from the first extruder anddecouple the first follower from the working surface of the cam as thesupport lowers the working surface of the cam adjacent to the firstfollower.

Implementations may include one or more of the following features. Theworking surface of the cam may be movable relative to the first extruderin response to a force associated with engagement of the support withthe cam. The first extruder may include a second follower movable alongthe damper, and the z-axis load from the first extruder may bereceivable by the damper via the second follower. The damper may includea contact surface for the second follower, the contact surface shaped tosmoothly lower the first extruder into a working position along thez-axis as the first extruder moves away from the support along thex-axis or y-axis. The first follower may be movable along the workingsurface of the cam in rolling contact with the working surface of thecam, and the second follower may be movable along the damper in rollingcontact with the support. The first follower and the second follower maybe spaced apart from one another at least along the z-axis. The extruderassembly may further include a gantry and a carriage, where the gantryhas a guide surface defining an axis perpendicular to the z-axis, thefirst extruder is supported on the carriage, and the carriage is movablealong the guide surface of the gantry in at least one direction alongthe axis perpendicular to the z-axis. At least one of the damper or thesupport may be in a fixed location along the axis perpendicular to thez-axis. The extruder assembly may further include a second extrudersupported on the carriage, where the second extruder defines a secondextrusion path, and movement of the first follower along the workingsurface of the cam changes a z-axis position of the first extruder. Theworking surface of the cam may be movable relative to the first extruderalong the axis perpendicular to the z-axis. The damper may include anarm cantilevered from the support along the axis perpendicular to thez-axis. The cam may be a linear cam, and the working surface of the cammay have a first two-dimensional profile in a plane defined by thez-axis and the axis perpendicular to the z-axis. The arm may have asecond two-dimensional profile in the plane defined by the z-axis andthe axis perpendicular to the z-axis, the first extruder may include asecond follower, and the arm may be engageable with the second followerto move the second follower along the second two-dimensional profile ofthe arm as the z-axis load of the first extruder is supported on thearm. The first two-dimensional profile of the working surface of the cammay be different from the second two-dimensional profile of the arm.

In one aspect, a three-dimensional printer disclosed herein includes abuild plate having a substantially planar surface, and a plurality ofextruders, each of the plurality of extruders defining a respectiveextrusion orifice directed toward the build plate, and each extrusionorifice supported above the build plate at a respective height along az-axis perpendicular to the substantially planar surface. Thethree-dimensional printer also includes a cam having a working surfaceengageable with a first extruder of the plurality of extruders, theworking surface of the cam moveable relative to the first extruder tochange a z-axis position of the first extruder relative to at least oneother one of the plurality of extruders. The three-dimensional printeralso includes a support engageable with the cam to move the cam in amanner that lowers the working surface supporting the first extruder,and a damper coupled to the support, the damper engageable with thefirst extruder to receive a z-axis load from the extruder therebydecoupling the first extruder from the cam as the contact with thesupport lowers the working surface.

Implementations may include one or more of the following features. Theplurality of extruders and the cam may be movable together in a firstdirection parallel to the substantially planar surface of the buildplate, the support may be selectively engageable with the cam to movethe cam relative to the plurality of extruders in a second direction,opposite the first direction, and a movement of the cam relative to thefirst extruder in the second direction may decouple the first extruderfrom the cam. The damper may include an arm cantilevered from thesupport in a direction parallel to the substantially planar surface ofthe build plate. The arm may include an inclined surface extendingobliquely to the substantially planar surface, the inclined surfacepositioned to make an initial contact with the first extruder as thedamper engages the first extruder, where the z-axis load of the firstextruder is received by the arm as the first extruder moves toward thesupport and away from the build plate along the inclined surface. Theinclined surface may include a first surface angled to receive a loadfrom the first extruder as the plurality of extruders move toward thesupport and a second surface angled to smoothly and continuously lowerthe first extruder into a working position as the plurality of extrudersmove away from the support.

In one aspect, a method disclosed herein includes moving a plurality ofextruders within a plane parallel to a substantially planar surface of abuild plate, each of the plurality of extruders defining a respectiveextrusion orifice supported above the build plate at a respective heightabove the substantially planar surface; moving a working surface of acam relative to a first extruder of the plurality of extruders, movementof the working surface changing a z-axis position of the first extruderrelative to the build plate; and engaging a damper with the firstextruder to receive a z-axis load from the first extruder. The pluralityof extruders and the cam may move together in a first direction, wherethe method further includes engaging a support with the cam to move thecam in a second direction, opposite the first direction, to providemovement of the working surface.

In one aspect, an extruder assembly disclosed herein includes a firstextruder defining a first extrusion path, at least one portion of thefirst extrusion path defining a z-axis, the first extruder including aworking surface shaped to translate a horizontal movement along theworking surface into a vertical movement of the first extruder. Theextruder assembly also includes a cam having a first followerhorizontally movable relative to the first extruder and positioned totravel along the working surface, the first follower movable along theworking surface of the first extruder as the first follower moves in afirst direction relative to the first extruder to lower the workingsurface along the z-axis. The extruder assembly also includes a supportengageable with the cam to move the cam in a second direction opposingthe first direction to raise the working surface along the z-axis, and adamper engageable with the first extruder to receive a z-axis load fromthe first extruder and to decouple the first follower from the workingsurface as the support lowers the working surface beneath first followerin response to a movement in the first direction.

In another aspect, an extruder assembly disclosed herein includes afirst extruder, a second extruder movably coupled to the first extruderto permit vertical movement of the second extruder relative to the firstextruder, and a coupler structurally configured to mechanically controla z-axis position of the second extruder relative to the first extruder,the coupler including a horizontal slider structurally configured tocause upward movement of the second extruder in response to a firsthorizontal movement in a first direction and to permit downward movementof the second extruder in response to a second horizontal movement in asecond direction opposing the first direction.

Implementations may include one or more of the following features. Thecoupler may extend horizontally from the extruder assembly to expose afirst end and a second end that provide control surfaces to move thecoupler horizontally in the first direction and the second directionrespectively. The extruder assembly may further include a support in apredetermined position within a three-dimensional printer, the supportincluding a first surface and a second surface, the first surface shapedto receive and vertically support the second extruder as the extruderassembly horizontally contacts the support, and the second surfaceshaped to concurrently move the coupler in the second direction as theextruder assembly horizontally contacts the support. The coupler or thesecond extruder may include a working surface with a ramp shaped togradually raise and lower the second extruder between an active positionwith an exit orifice below a lowest point of the first extruder and aninactive position with the exit orifice above the lowest point of thefirst extruder. The working surface may include a plateau above the rampto support the second extruder in the inactive position and a ridge, theridge having a height greater than the plateau and the ridge positionedbetween the plateau and the ramp to bi-stably retain the second extruderin the inactive position when the extruder assembly is not engaged withthe damper.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the devices,systems, and methods described herein will be apparent from thefollowing description of particular embodiments thereof, as illustratedin the accompanying drawings. The drawings are not necessarily to scale,emphasis instead being placed upon illustrating the principles of thedevices, systems, and methods described herein. In the drawings, likereference numerals generally identify corresponding elements.

FIG. 1 is a block diagram of a three-dimensional printer.

FIG. 2 shows an extruder assembly with a first extruder in a ‘down’position.

FIG. 3 shows an extruder assembly with a first extruder in an ‘up’position.

FIG. 4 shows a cam engaged with followers in multiple positions todemonstrate moving an extruder of an extruder assembly from a ‘down’position to an ‘up’ position.

FIG. 5 shows a cam engaged with followers in multiple positions todemonstrate moving an extruder of an extruder assembly from an ‘up’position to a ‘down’ position.

FIG. 6 shows an extruder assembly including a support.

FIG. 7 shows a support engaged with a follower.

FIG. 8 shows a detail of a support engaged with a follower.

FIG. 9 shows a side view of an extruder in an ‘up’ position.

FIG. 10 shows a side view of an extruder in a ‘down’ position.

FIG. 11 is a flowchart of a method for changing a z-axis position of anextruder in an extruder assembly featuring a plurality of extruders.

FIG. 12 shows an extruder assembly with a first extruder in a ‘down’position.

FIG. 13 shows an extruder assembly with a first extruder in an ‘up’position.

DESCRIPTION

Embodiments will now be described with reference to the accompanyingfigures. The foregoing may, however, be embodied in many different formsand should not be construed as limited to the illustrated embodimentsset forth herein.

All documents mentioned herein are hereby incorporated by reference intheir entirety. References to items in the singular should be understoodto include items in the plural, and vice versa, unless explicitly statedotherwise or clear from the text. Grammatical conjunctions are intendedto express any and all disjunctive and conjunctive combinations ofconjoined clauses, sentences, words, and the like, unless otherwisestated or clear from the context. Thus, the term “or” should generallybe understood to mean “and/or” and so forth.

Recitation of ranges of values herein are not intended to be limiting,referring instead individually to any and all values falling within therange, unless otherwise indicated herein, and each separate value withinsuch a range is incorporated into the specification as if it wereindividually recited herein. The words “about,” “approximately” or thelike, when accompanying a numerical value, are to be construed asindicating a deviation as would be appreciated by one of ordinary skillin the art to operate satisfactorily for an intended purpose. Similarly,words of approximation such as “approximately” or “substantially” whenused in reference to physical characteristics, should be understood tocontemplate a range of deviations that would be appreciated by one ofordinary skill in the art to operate satisfactorily for a correspondinguse, function, purpose, or the like. Ranges of values and/or numericvalues are provided herein as examples only, and do not constitute alimitation on the scope of the described embodiments. Where ranges ofvalues are provided, they are also intended to include each value withinthe range as if set forth individually, unless expressly stated to thecontrary. The use of any and all examples, or exemplary language(“e.g.,” “such as,” or the like) provided herein, is intended merely tobetter illuminate the embodiments and does not pose a limitation on thescope of the embodiments. No language in the specification should beconstrued as indicating any unclaimed element as essential to thepractice of the embodiments.

In the following description, it is understood that terms such as“first,” “second,” “top,” “bottom,” “up,” “down,” and the like, arewords of convenience and are not to be construed as limiting termsunless specifically stated to the contrary.

Described herein are devices, systems, and methods for improvements inthree-dimensional printing, such as improvements related to extrudersand extrusion techniques.

The following description emphasizes three-dimensional printers usingfused deposition modeling or similar techniques where a bead of materialis extruded in a layered series of two dimensional patterns as “roads”or “paths” to form a three-dimensional object from a digital model. Itwill be understood, however, that numerous additive fabricationtechniques are known in the art including, without limitation, multijetprinting, stereolithography, Digital Light Processor (“DLP”)three-dimensional printing, selective laser sintering, and so forth.Such techniques may benefit from the systems and methods describedbelow, and all such printing technologies are intended to fall withinthe scope of this disclosure, and within the scope of terms such as“printer,” “three-dimensional printer,” “fabrication system,” and soforth, unless a more specific meaning is explicitly provided orotherwise clear from the context.

FIG. 1 is a block diagram of a three-dimensional printer. In general, aprinter 100 may include a build platform 102 (which may otherwise bereferred to herein as a “build plate”), a conveyor 104, an extruder 106,an x-y-z positioning assembly 108, and a controller 110 that cooperatewith one another to fabricate an object 112 within a working volume 114of the printer 100.

The build platform 102 may include a surface 116 that is rigid andsubstantially planar. The surface 116 may support the conveyer 104 toprovide a fixed, dimensionally and positionally stable platform on whichto build the object 112.

The build platform 102 may include a thermal element 130 that controlsthe temperature of the build platform 102 through one or more activedevices 132 such as thermoelectric heating and/or cooling devices (e.g.,resistive elements that convert electrical current into heat, Peltiereffect devices that can create a heating or cooling affect, andcombinations thereof). Accordingly, the thermal element 130 may be aheater that provides active heating to the build platform 102, a coolingelement that provides active cooling to the build platform 102, or acombination of these. The heater 130 may be coupled in a communicatingrelationship with the controller 110 for the controller 110 tocontrollably impart heat to or remove heat from the surface 116 of thebuild platform 102. Thus, for example, the thermal element 130 mayinclude an active cooling element positioned within or adjacent to thebuild platform 102 to controllably cool the build platform 102.

It will be understood that a variety of other techniques mayadditionally, or alternatively, be employed to control a temperature ofthe build platform 102. For example, the build platform 102 may use agas cooling or gas heating device such as a vacuum chamber in aninterior thereof, which may be quickly pressurized to heat the buildplatform 102 or vacated to cool the build platform 102 as desired. Asanother non-exclusive example, a stream of heated or cooled gas may beapplied directly to the build platform 102 before, during, and/or aftera build process.

The conveyer 104 may include a sheet 118 of material that moves in apath 120 through the working volume 114. Within the working volume 114,the path 120 may pass proximal to the surface 116 of the build platform102—that is, resting directly on or otherwise supported by the surface116—to provide a rigid, positionally stable working surface for a build.It will be understood that, while the path 120 is depicted as aunidirectional arrow, the path 120 may be bidirectional, such that theconveyer 104 can move, for example, in either of two opposing directionsthrough the working volume 114. It will also be understood that the path120 may curve in any of a variety of ways, such as by looping underneathand around the build platform 102, over and/or under rollers, or arounddelivery and take up spools for the sheet 118 of material. Thus, whilethe path 120 may be generally (but not necessarily) uniform through theworking volume 114, the conveyer 104 may move in any direction suitablefor moving completed items from the working volume 114. The conveyor 104may, additionally or alternatively, include a motor or other similardrive mechanism (not shown) coupled to the controller 110 to controlmovement of the sheet 118 of material along the path 120. Various drivemechanisms are described in further detail below.

In general, the sheet 118 may be formed of a flexible material such as amesh material, a polyamide, a polyethylene terephthalate (commerciallyavailable in bi-axial form as MYLAR), a polyimide film (commerciallyavailable as KAPTON), or any other suitably strong polymer or othermaterial. The sheet 118 may have a thickness of about three to aboutseven thousandths of an inch, or any other thickness that permits thesheet 118 to follow the path 120 of the conveyer 104. For example, withsufficiently strong material, the sheet 118 may have a thickness ofabout one to about three thousandths of an inch. The sheet 118 mayfurther, or instead, include sections of rigid material joined byflexible links.

A working surface of the sheet 118 (e.g., an area on the top surface ofthe sheet 118 within the working volume 114) may be treated to assistwith adhesion of build material to the surface 118 and/or to facilitateremoval of completed objects from the surface 118. For example, theworking surface may be abraded or otherwise textured (e.g., withgrooves, protrusions, and the like) to improve adhesion between theworking surface and the build material.

A variety of chemical treatments may be used on the working surface ofthe sheet 118 of material to facilitate build processes as describedherein. For example, the chemical treatment may include deposition ofmaterial that can be chemically removed from the conveyer 104 by use ofwater, solvents, or the like. This may facilitate separation of acompleted object from the conveyer by dissolving the layer of chemicaltreatment between the object 112 and the conveyor 104. The chemicaltreatments may include deposition of a material that easily separatesfrom the conveyer such as a wax, mild adhesive, or the like. Thechemical treatment may include a detachable surface such as an adhesivethat is sprayed onto the conveyer 104 prior to fabrication of the object112.

In one aspect, the conveyer 104 may include a sheet of disposable,one-use material fed from a dispenser and consumed with each successivebuild.

In one aspect, the conveyer 104 may include a number of differentworking areas with different surface treatments adapted for differentbuild materials or processes. For example, different areas may havedifferent textures (e.g., smooth, abraded, grooved, etc.). Additionally,or alternatively, different areas may be formed of different materials.Further, or instead, different areas may have or receive differentchemical treatments. Thus, it should be appreciated that a singleconveyer 104 may be used in a variety of different build processes byselecting the various working areas as needed or desired.

The extruder 106 may include a chamber 122 in an interior thereof toreceive a build material. The build material may, for example, includeacrylonitrile butadiene styrene (“ABS”), high-density polyethylene(“HDPL”), polylactic acid, or any other suitable plastic, thermoplastic,or other material that can usefully be extruded to form athree-dimensional object. The extruder 106 may include an extrusion tip124 defining an exit port with a circular, oval, slotted or othercross-sectional profile that extrudes build material in a desiredcross-sectional shape.

The extruder 106 may include a heater 126 to melt build materials (e.g.,thermoplastic material) within the chamber 122 for extrusion through theextrusion tip 124 in melted form. While illustrated in block form, itwill be understood that the heater 126 may include, e.g., coils ofresistive wire wrapped about the extruder 106, one or more heatingblocks with resistive elements to heat the extruder 106 with appliedcurrent, an inductive heater, or any other arrangement of heaterssuitable for creating heat within the chamber 122 to melt the buildmaterial for extrusion. The extruder 106 may also, or instead, include amotor 128 to push the build material into the chamber 122, through theextrusion tip 124, or a combination thereof.

In general operation (and by way of example rather than limitation), abuild material, such as ABS plastic in filament form, may be fed intothe chamber 122 from a spool by the motor 128, melted by the heater 126,and extruded from the extrusion tip 124. By controlling processparameters (e.g., one or more of a rate of the motor 128 and thetemperature of the heater 126) the build material may be extruded at acontrolled volumetric rate. It will be understood that a variety oftechniques may be employed to deliver build material at a controlledvolumetric rate, which may depend upon the type of build material, thevolumetric rate desired, and any other factors. All such techniques thatmight be suitably adapted to delivery of build material for fabricationof a three-dimensional object are intended to fall within the scope ofthis disclosure. Other techniques may be employed for three-dimensionalprinting, including extrusion-based techniques using a build materialthat is curable and/or a build material of sufficient viscosity toretain shape after extrusion.

The x-y-z positioning assembly 108 may generally be movable tothree-dimensionally position the extruder 106 and the extrusion tip 124within the working volume 114. Thus, for example, by controlling thevolumetric rate of delivery for the build material and the x, y, zposition of the extrusion tip 124, the object 112 may be fabricated inthree dimensions by depositing successive layers of material intwo-dimensional patterns derived (e.g., two-dimensional patterns derivedfrom cross-sections of a computer model or other computerizedrepresentation of the object 112). The x-y-z positioning assembly 108may, for example, include a number of stepper motors 109 to controlindependently a position of the extruder within the working volume alongeach of an x-axis, a y-axis, and a z-axis. More generally, the x-y-zpositioning assembly 108 may include, without limitation, variouscombinations of stepper motors, encoded DC motors, gears, belts,pulleys, worm gears, threads, and the like. Any such arrangementsuitable for controllably positioning the extruder 106 within theworking volume 114 may be adapted to use with the printer 100 describedherein.

By way of example and not limitation, the conveyor 104 may be affixed toa bed that provides x-y positioning within the plane of the conveyor104, while the extruder 106 can be independently moved along a z-axis.Additionally, or alternatively, the conveyor 104 may be x, y, and zpositionable, and the extruder 106 may be, optionally, stationary.Further, or instead, the extruder 106 may be x, y, and z positionablewhile the conveyer 104 remains fixed (relative to the working volume114). In yet another example, the conveyer 104 may, by movement of thesheet 118 of material, control movement in one axis (e.g., the y-axis),while the extruder 106 moves in the z-axis as well as one axis in theplane of the sheet 118. Thus, in certain instances, the conveyor 104 maybe attached to and move with at least one of an x-axis stage (thatcontrols movement along the x-axis), a y-axis stage (that controlsmovement along a y-axis), and a z-axis stage (that controls movementalong a z-axis) of the x-y-z positioning assembly 108. More generally,any arrangement of motors and other hardware controllable by thecontroller 110 may serve as the x-y-z positioning assembly 108 in theprinter 100 described herein. Still more generally, while an x, y, zcoordinate system may serve as a convenient basis for positioning withinthree dimensions, any other coordinate system or combination ofcoordinate systems may also or instead be employed, such as a positionalcontroller and assembly that operates according to cylindrical orspherical coordinates.

The controller 110 may be electrically coupled in a communicatingrelationship with the build platform 102, the conveyer 104, the x-y-zpositioning assembly 108, and the other various components of theprinter 100. In general, the controller 110 is operable to control thecomponents of the printer 100, such as the build platform 102, theconveyer 104, the x-y-z positioning assembly 108, and any othercomponents of the printer 100 described herein to fabricate the object112 from the build material. The controller 110 may include anycombination of software and/or processing circuitry suitable forcontrolling the various components of the printer 100 described hereinincluding, without limitation, microprocessors, microcontrollers,application-specific integrated circuits, programmable gate arrays, andany other digital and/or analog components, as well as combinations ofthe foregoing, along with inputs and outputs for transceiving controlsignals, drive signals, power signals, sensor signals, and the like. Inone aspect, the controller 110 may include a microprocessor or otherprocessing circuitry with sufficient computational power to providerelated functions such as executing an operating system, providing agraphical user interface (e.g., to a display coupled to the controller110 or printer 100), convert three-dimensional models into toolinstructions, and operate a web server or otherwise host remote usersand/or activity through a network interface 136 described below.

A variety of additional sensors may be usefully incorporated into theprinter 100 described above. These are generically depicted as sensor134 in FIG. 1, for which the positioning and mechanical/electricalinterconnections with other elements of the printer 100 will depend uponthe type and purpose of the sensor 134 and will be readily understoodand appreciated by one of ordinary skill in the art. The sensor 134 mayinclude a temperature sensor positioned to sense a temperature of thesurface of the build platform 102. This may, for example, include athermistor embedded within or attached below the surface of the buildplatform 102. This may also or instead include an infrared detectordirected at the surface 116 of the build platform 102 or the sheet 118of material of the conveyer 104. Other sensors that may be usefullyincorporated into the printer 100 as the sensor 134 include, withoutlimitation, a heat sensor, a volume flow rate sensor, a weight sensor, asound sensor, and a light sensor. Certain more specific examples areprovided below by way of example and not of limitation.

The sensor 134 may include a sensor to detect a presence (or absence) ofthe object 112 at a predetermined location on the conveyer 104. This mayinclude an optical detector in a beam-breaking configuration to sensethe presence of the object 112 at a location such as an end of theconveyer 104. This may also or instead include an imaging device andimage processing circuitry to capture an image of the working volume 114and analyze the image to evaluate a position of the object 112. Thissensor 134 may be used, for example, to ensure that the object 112 isremoved from the conveyor 104 prior to beginning a new build at thatlocation on the working surface (e.g., the surface 116 of the buildplatform 102). Thus, the sensor 134 may be used to determine whether anobject is present that should not be, or to detect when an object isabsent, or a combination thereof. The feedback from this sensor 134 maybe used by the controller 110 to issue processing interrupts orotherwise control operation of the printer 100.

The sensor 134 may include a sensor that detects a position of theconveyer 104 along the path. This information may be obtained, forexample, from an encoder in a motor that drives the conveyer 104, orusing any other suitable technique such as a visual sensor andcorresponding fiducials (e.g., visible patterns, holes, or areas withopaque, specular, transparent, or otherwise detectable marking) on thesheet 118.

The sensor 134 may include a heater (e.g., a radiant heater or forcedhot air) to heat the working volume 114 to maintain the object 112 at afixed, elevated temperature throughout a build. The sensor 134 may also,or instead, include a cooling element to maintain the object 112 at apredetermined sub-ambient temperature throughout a build. It should beappreciated that a heater included in the sensor 134 may be instead of,or in addition to, the thermal element 130.

The sensor 134 may also or instead include at least one video camera.The video camera may generally capture images of the working volume 114,the object 112, or any other hardware associated with the printer 100.The video camera may provide a remote video feed through the networkinterface 136. In such instances, the feed may be available to remoteusers through a user interface maintained, for example, by remotehardware, or, further or instead, the feed may be available within a webpage provided by a web server hosted by the three-dimensional printer100. Thus, in certain implementations, there is a user interface adaptedto present a video feed from at least one video camera of athree-dimensional printer to a remote user through a user interface.

The sensor 134 may also or instead include more complex sensing andprocessing systems or subsystems, such as a three-dimensional scannerusing optical techniques (e.g., stereoscopic imaging, or shape frommotion imaging), structured light techniques, or any other suitablesensing and processing hardware that might extract three-dimensionalinformation from the working volume 114. In some instances, the sensor134 may include a machine vision system that captures images andanalyzes image content to obtain information about the status of a job,working volume 114, or an object 112 therein. The machine vision systemmay support a variety of imaging-based automatic inspection, processcontrol, and/or robotic guidance functions for the three-dimensionalprinter 100 including, without limitation, pass/fail decisions, errordetection (and corresponding audible or visual alerts), shape detection,position detection, orientation detection, collision avoidance, andcombinations thereof.

The printer 100 may include other hardware 135, which may be, forexample, input devices including any one or more of the following: akeyboard, a touchpad, a mouse, switches, dials, buttons, and motionsensors. Additionally, or alternatively, the other hardware 135 may be,for example, output devices including any one or more of the following:a display, a speaker or other audio transducer, and light emittingdiodes. Other hardware 135 may also or instead include a variety ofcable connections and/or hardware adapters for connecting, for example,to external computers, external hardware, external instrumentation dataacquisition systems, and combinations thereof.

The printer 100 may include, or be connected in a communicatingrelationship with, the network interface 136. The network interface 136may include any combination of hardware and software suitable forcoupling the controller 110 and other components of the printer 100 to aremote computer in a communicating relationship through a data network.By way of example and not limitation, this may include electronics for awired or wireless Ethernet connection operating according to the IEEE802.11 standard (or any variation thereof), or any other short orlong-range wireless networking components. This may include hardware forshort range data communications such as Bluetooth or an infraredtransceiver, which may be used to couple into a local area network thatis, in turn, coupled to a data network such as the Internet. This mayalso, or instead, include hardware/software for a WiMAX connection or acellular network connection (using, e.g., CDMA, GSM, LTE, or any othersuitable protocol or combination of protocols). The controller 110 maybe configured to control participation by the printer 100 in any networkto which the network interface 136 is connected, such as by autonomouslyconnecting to the network to retrieve printable content, or respondingto a remote request for status or availability.

Specific improvements to three-dimensional printing, e.g., using athree-dimensional printer as described above with reference to FIG. 1,will now be discussed. One such improvement may include a system forchanging the z-axis position of one or more extruders in amulti-extruder assembly, and another such improvement may includemechanical damping that mitigates noise and vibration by graduallytransferring a vertical load while a movable extruder is being loweredinto a position for printing. In this manner, the present teachings maygenerally include a cam that acts as a “toggle” for an extruder assemblyfeaturing multiple extruders. Specifically, an extruder assembly mayinclude a two-sided toggle (e.g., for two extruders) as well as dampingfor noise and vibration that can be created by such a two-sided toggle.

FIG. 2 shows an extruder assembly with a first extruder in a ‘down’position, and FIG. 3 shows the extruder assembly with the first extruderin an ‘up’ position. The extruder assembly 200 may include a pluralityof extruders—e.g., a first extruder 201 and a second extruder 202—whereany of these individual extruders may include any of the features of theextruder 106 of FIG. 1 described above. In other words, unless otherwisespecified or made clear from the context, the extruder assembly 200should be understood to be interchangeable with the extruder 106discussed above with respect to FIG. 1.

In general, a three-dimensional printer having a build volume with anx-axis (which would be traversing into and out of the page in FIGS. 1and 2), a y-axis 204, and a z-axis 205 may feature an extruder assembly200 including a plurality of extruders. It will be understood that,unless explicitly stated to the contrary or otherwise clear from thecontext, when referring to movement of the extruder assembly 200 or itscomponents along the y-axis 204, this could also or instead includemovement along the x-axis. That is, in general, the present teachingsmay include an extruder assembly 200 that moves along one or more of thex-axis and y-axis 204 to move one of the extruders along a z-axis 205.

The extruder assembly 200 (or, more generally, a three-dimensionalprinter) may include a multi-extruder including a first extruder 201 anda second extruder 202, a plurality of followers (e.g., a first follower210 and a second follower 212), a cam 220, a support, and a dampercoupled to the support (although not shown in FIGS. 2 and 3, the support670 and the damper 680 are shown in, e.g., FIGS. 6 and 7).

Turning back to FIGS. 2 and 3, one or more of the first extruder 201 andthe second extruder 202 may be movable along the z-axis 205 relative toa gantry or a carriage 250 that holds the extruder assembly 200 (e.g.,where the carriage 250 is movable via an x-y-z positioning assembly suchas that described above). For example, each of the first extruder 201and the second extruder 202 may be movable, or one of these extrudersmay be fixed while the other is movable. By way of example, in animplementation, the first extruder 201 is movably coupled to thethree-dimensional printer to permit a change of position of the firstextruder 201 in a direction of the z-axis 205 independent from thesecond extruder 202, while the second extruder 202 remains in a fixedz-axis position. In this manner, one or more of the extruders may beindependently movable along the z-axis 205 relative to the other(s), orthe extruders may cooperate with one another when moving along thez-axis 205.

The first extruder 201 may define a first extrusion path 206 through afirst extrusion orifice 208 of the first extruder 201, where at leastone portion of the first extrusion path 206 is disposed along the z-axis205. Similarly, the second extruder 202 may define a second extrusionpath 207 through a second extrusion orifice 209 of the second extruder202, where at least one portion of the second extrusion path 207 isdisposed along the z-axis 205.

The first extruder 201 may include, or otherwise be coupled to, one ormore followers—e.g., a first follower 210 and a second follower 212. Thefollowers may include a bearing, a wheel, or the like, where thefollowers can freely rotate about an axis (e.g., an axis aligned alongthe x-axis), but where the axis of the followers is fixed relative tothe first extruder 201. In general, the followers may include a loadbearing surface oriented to permit relatively low-friction movementalong the x-axis or the y-axis 604. That is, the followers may bestructurally configured to rotate and follow along a surface, such as aworking surface 222 of the cam 220.

The position of each of the first follower 210 and the second follower212 relative to the first extruder 201 may be fixed. That is, becausethe followers may include a bearing or a wheel, the followers may becapable of rotating, while other movement relative to the extruders ismechanically discouraged or prevented. In this manner, if one or more ofthe first follower 210 and the second follower 212 are moved (e.g.,along the z-axis 205), then the first extruder 201 (or a portion of thecarriage 250 holding the first extruder 201) may similarly be moved.More succinctly, in certain implementations, if the followers experienceat least a predetermined force along the z-axis 205, both the followersand the first extruder 201 will move along the z-axis 205.

Thus, the first follower 210 may be structurally configured to adjustthe z-axis position of the first extruder 201. That is, when the firstfollower 210 is raised (e.g., by the working surface 222 of the cam220), the first extruder 201 may be similarly raised, and vice-versa.

In general, the second follower 212 may be structurally configured todampen a lowering of the first extruder 201 from a non-printing heightto a printing height along the z-axis 205. That is, because of thematerials used (e.g., metals) and the weight of the extruders, loweringthe first extruder 201 from a non-printing height to a printing heightalong the z-axis 205 may result in unwanted noise or vibration. Tomitigate this, the second follower 212 may be positioned andstructurally configured to move along another surface (e.g., the surfaceof a damper), which may be ramped or otherwise shaped to bear at least aportion of the z-axis load of the first extruder 201 and to graduallytransfer this load to a different z-axis position when transitioningfrom the non-printing height to the printing height along the z-axis 205or when otherwise decoupling the first follower 210 from the workingsurface 222 of the cam 220.

The cam 220 may include an elongate member that extends through one ormore of the first extruder 201 and the second extruder 202 (e.g., thecam 220 may extend through each of the extruders in an extruder assembly200). Also, or instead, the cam 220 may extend through and be coupledwith the carriage 250 that holds one or more of the first extruder 201and the second extruder 202. The cam 220 may be movable (e.g., slidable)relative to one or more of the first extruder 201 and the secondextruder 202. That is, the cam 220 may have a working surface 222movable relative to the first extruder 201, for example, where theworking surface 222 is the top surface of an elongate body that formsthe cam 220. The working surface 222 may be shaped to translate a firstmovement of the cam 220 along one or more of the x-axis or the y-axis205 into a second movement of the first follower 210 along the z-axis205. In this manner, the first follower 210 may be movable along theworking surface 222 of the cam 220 as the working surface 222 movesrelative to the first extruder 201 to raise the first follower 210 alongthe z-axis 205. And because the axis of the first follower 210 may befixed relative to the first extruder 201, movement of the first follower210 along the z-axis 205 may similarly move the first extruder 201 alongthe z-axis 205.

The cam 220 may therefore act as a toggle for the extruder assembly 200,with the ability to adjust a z-axis height of one or more extruders ofthe extruder assembly—e.g., between a printing height for depositingbuild material in a three-dimensional print and a non-printing heightwhen an extruder is not depositing build material in a three-dimensionalprint. The working surface 222 of the cam 220 may be shaped to lift thefirst extruder 201 (or the second extruder 202) along the z-axis 205 viathe first follower 210 when the cam 220 moves in a first direction alongthe y-axis 204 (or another axis intersecting the z-axis 205).

As stated above, the cam 220 may extend through each of the firstextruder 201 and the second extruder 202 such that each of a first end223 and a second end 224 of the cam 220 is exposed external to themulti-extruder extruder assembly 200. In this manner, either of thefirst end 223 and the second end 224 of the cam 220 may be contactedfrom outside the multi-extruder assembly 200 to move the cam 220vertically in either direction relative to the multi-extruder assembly200. In certain implementations, the cam 220 is in communication with aslider 226 or the like (e.g., one or more bearings) that facilitatessliding movement of the cam 220 relative to the extruders of theextruder assembly 200.

In certain implementations, a biasing member 230 such as a spring may becoupled to one or more of the first extruder 201 and the second extruder202, or a component engaged thereto. The biasing member 230 may bestructurally configured to bias one or more of the first extruder 201and the second extruder 202 toward either a printing height or anon-printing height along the z-axis 205, e.g., in the absence of otherforces such as the force of the working surface 222 of the cam 220against the first follower 210. This may, for example, mitigate rattlingof individual extruders as the multi-extruder assembly 200 is movedabout within a build volume during use.

The extruder assembly 200 may further include one or more drive wheels240. In certain implementations, a single drive wheel 240 may be sharedby each of the first extruder 201 and the second extruder 202 fordriving a build material (e.g., a filament) therethrough. To this end, adisplacement of the drive wheel 240 (e.g., along the z-axis 205) mayalternately disengage or engage with one of the first extruder 201 andthe second extruder 202. In another aspect, the drive wheel 240 may beclutched or otherwise mechanically configured to that a clockwiserotation of the drive wheel 240 advances one extruder while acounterclockwise rotation of the drive wheel 240 advances the other. Inother implementations, such as that shown in FIGS. 2 and 3, eachextruder may include its own drive wheel 240.

As discussed above, the cam 220 may work in conjunction with the firstfollower 210 for moving a z-axis position of the first extruder 201. Forexample, and as discussed above, FIG. 2 shows an extruder assembly 200with the first extruder 201 in a down position, and FIG. 3 shows theextruder assembly 200 with the first extruder 201 in an up position,where the down position is a printing position and the up position is anon-printing position. That is, when the first extruder 201 is in thedown position, it may be positioned for depositing build material in athree-dimensional printing operation while the second extruder 202 is inthe up position (relative to the first extruder 20—as noted, the secondextruder 202 may remain stationary along the z-axis 205 while the firstextruder 201 moves up and down) while inactive, e.g., while notdepositing build material in the three-dimensional printing operation;and when the first extruder 201 is in the up or inactive position, thesecond extruder 202 may be in an active position relative to the firstextruder 201 for depositing build material in the three-dimensionalprinting operation. In certain implementations, only one of theextruders is capable of moving between the up position and the downposition, while another extruder remains fixed at a predetermined z-axisheight relative to the carriage 250. In other implementations, each ofthe extruders in the extruder assembly 200 is capable of moving betweenthe up position and the down position. For example, when one extrudermoves (e.g., from the up position to the down position), the otherextruder may automatically move in the opposite direction along thez-axis 205 (e.g., from the down position to the up position), e.g. bycoupling the two extruders through a pivot that enforces alternatez-axis movement, or otherwise controlling or interconnecting the twoextruders for opposing vertical motion.

It will be understood that the difference between the down position andthe up position may be relatively small. For example, in certainimplementations, the difference in the z-axis height between the upposition and the down position for the end of the extruder that depositsbuild material is between about 1-2 mm (e.g., about 1.4 mm), or enoughvertical displacement to avoid interference between a lowest point ofthe inactive extruder and a highest point of build material deposited bythe active extruder. FIGS. 2 and 3 demonstrate this z-axis heightdifference by showing the difference in z-axis height between the axlesof the first follower 210 in the first extruder 201 and the drive wheel240 of the second extruder 202. That is, the distance D1 in FIG. 2 showsthe difference in z-axis height between the axles of the first follower210 in the first extruder 201 when the first extruder 201 is in the downposition; and distance D2 in FIG. 3 shows the difference in z-axisheight between the axles of the first follower 210 in the first extruder201 when the first extruder 201 is in the up position. Specifically, D1may be larger than D2, demonstrating that the z-axis position of thefirst extruder 201 is located further away from the drive wheel 240 ofthe second extruder 202 (which may have a fixed z-axis position relativeto the carriage 250) in the down position. In certain implementations,D1 is about 12.600 mm and D2 is about 11.194 mm. However, otherdistances are also or instead possible for D1 and D2.

FIG. 4 shows a cam engaged with followers in multiple positions todemonstrate moving an extruder of an extruder assembly from a ‘down’position (or active position or printing height) to an ‘up’ position (orinactive position or non-printing height). The cam 420 and the follower410 shown in this figure may be the same as, or similar to, the cam 220and first follower 210 discussed above with reference to FIGS. 2 and 3.

Turning back to FIG. 4, as shown in phase one 401, in the down positionof an extruder that includes, or is engaged with, the follower 410 thatis structurally configured to traverse along the working surface 422 ofthe cam 420, the follower 410 may be disposed in a position adjacent to(and not on) a plateau 426 of the working surface 422 (e.g., disposed ata peak of the working surface 422). The position of the follower 410 maybe fixed relative to the extruder, but the follower 410 may bestructurally configured to rotate about an axis 411—thus, the positionof the axis 411 may be fixed relative to the extruder, where movement ofthe follower 410 (other than the rotation of the follower 410) may causea corresponding movement of the extruder.

As shown in phase two 402, when the cam 420 is moved in a firstdirection 432, the follower 410 may move in a second direction 434 alongthe working surface 422 of the cam 420 from a first position 410 a to asecond position 410 b. That is, the follower 410 may move along theworking surface 422 toward the first end 423 of the cam 420 and awayfrom the second end 424 of the cam 420. This movement of the follower410 in the second direction 434 may cause the follower 410 to traverseup a ramped portion 428 of the working surface 422 in the seconddirection 434 toward the plateau 426 of the working surface 422. Thismovement may cause a change in the z-axis position of the follower 410(and thus the extruder to which it is fixedly engaged), where the changein the z-axis position of the follower 410 corresponds to the z-axisheight difference between a region of the working surface 422 disposedbelow the plateau 426 (e.g., a region on or below the ramped portion428) and the plateau 426 of the working surface 422. This z-axis heightchange is demonstrated by the first position 410 a and the secondposition 410 b of the follower 410 shown in phase two 402.

Phase three 403 shows the follower 410 in an up position. Specifically,in phase three 403, the z-axis height position of the follower 410 maybe located above its z-axis height position in phase one 401,demonstrating that the z-axis height of the follower 410 (and thus theextruder to which it is fixedly engaged) may change between the downposition shown in phase one 401 and the up position shown in phase three403. Further, in phase three 403, in the up position of the extruderthat is engaged to the follower 410, the follower 410 may be disposed ina position on the plateau 426 of the working surface 422. In thisposition, movement of the cam 420 in the second direction 434 may causethe follower 410 to revert back to its position shown in phase one 401.

It will also be noted that the cam 420 may include a ridge 430 or othersimilar feature to provide a bi-stable position for the follower 410 onthe plateau 426. This may help to prevent the cam 420 from drifting inan opposite direction and releasing the follower 410 during use before aforce is applied to the second end 424 of the cam 420 to purposefullylower the follower 410 and the associated extruder into an activeposition. That is, the working surface 422 may include the plateau 426disposed above the ramped portion 428 to support an extruder in aninactive, non-printing position. The working surface 422 may furtherinclude the ridge 430 having a height greater than the plateau 426.Specifically, the ridge 430 may be positioned between the plateau 426and the ramped portion 428 to bi-stably retain an extruder in theinactive position (e.g., when the extruder is not engaged with thedamper as described herein). However, inclusion of the ridge 430,although useful for maintaining a position of the follower on theplateau 426 as shown in phase three 403, may cause the follower 410 to“hop” over the ridge 430 when traversing to the down position. Suchhopping may cause unwanted noise and vibration that can eventuallydamage components of an extruder assembly or three-dimensional printer.Thus, one or more of a support and a damper as described elsewhereherein may be advantageously included for use with such an extruderassembly to, inter alia, mitigate such unwanted noise and vibration.

FIG. 5 shows a cam engaged with followers in multiple positions todemonstrate moving an extruder of an extruder assembly from an ‘up’position to a ‘down’ position. The cam 420 in FIG. 5 may be the same asthat described above with reference to FIG. 4, and thus the samereference numerals are generally used for these figures. Morespecifically, while FIG. 4 demonstrates movement of the follower 410from a lower z-axis height position to a higher z-axis height position,FIG. 5 shows the converse—i.e., movement of the follower 410 from ahigher z-axis height position to a lower z-axis height position.

Phase three 403 of FIG. 5 is the same as phase three 403 shown in FIG.4, where the follower 410 is disposed in an up position, e.g., on thepeak 426 of the working surface 422 of the cam 420. As stated above, andas demonstrated by phase four 404 and phase five 405 described below,movement of the cam 420 in the second direction 434 may cause thefollower 410 to revert back to a down position.

As shown in phase four 404, when the cam 420 is moved in the seconddirection 434, the follower 410 may move in the first direction 432along the working surface 422 of the cam 420 from the second position410 b to the first position 410 a. That is, the follower 410 may movealong the working surface 422 toward the second end 424 of the cam 420and away from the first end 423 of the cam 420. This movement of thefollower 410 in the first direction 432 may cause the follower 410 totraverse down the ramped portion 428 of the working surface 422 in thefirst direction 432, i.e., off of and away from the plateau 426 of theworking surface 422.

Phase five 405 represents the down position for the follower 410 (andthus the extruder to which it may be fixedly engaged), where phase five405 may be the same as phase one 401 of FIG. 4.

It will be understood that such a downward movement in FIG. 5 of thefollower 410 and the extruder (or carriage) to which it is engaged canbe noisy and/or may cause undesired vibrations. Thus, the presentteachings may include features to mitigate such noise and vibration. Onesuch feature may include the size and shape of the working surface 422itself. That is, by including a ramped portion 428 (or another similarfeature) that has a relatively shallow slope/incline, an extruder can begradually lowered into an active position, and the accompanyingmechanical noise and vibration can be mitigated. Additional oralternative features to mitigate such noise and vibration are describedbelow.

FIG. 6 shows an extruder assembly including a support, and FIG. 7 showsthe support engaged with a follower. Specifically, these figures show acarriage 650 of an extruder assembly 600 (which may be the same orsimilar to any of the extruder assemblies described herein), a gantry660, and a support 670. FIG. 6 may represent an up position for a firstextruder in the carriage 650, while FIG. 7 may represent moments beforethe first extruder is disposed in a down position. In general, thesupport 670 and a corresponding damper 680 may be used to mitigate noiseand/or vibration when moving an extruder of the extruder assembly 600along one or more axes. Also, or instead, the support 670 may be used inconjunction with the cam 620 to raise and lower an extruder of theextruder assembly 600.

The carriage 650 may be structurally configured to hold or otherwisecouple with one or more extruders of the extruder assembly 600—e.g., thecarriage 650 of the exemplary embodiment in FIGS. 6 and 7 may bestructurally configured to couple with two extruders. Specifically, thecarriage 650 may include one or more sub-carriages each structurallyconfigured for housing or otherwise coupling to an extruder. Forexample, the carriage 650 of FIGS. 6 and 7 includes a first sub-carriage651 and a second sub-carriage 652, which may be structurally configuredto engage with the first extruder and the second extruder, respectively,such as the first extruder and the second extruder described above.Thus, the carriage 650 may be structurally configured to receive one ormore modular extruders therein, e.g., within one or more cavities 654defined by a structure of the carriage 650. In this manner, a firstextruder may be supported on the carriage 650, where the first extruderdefines a first extrusion path, and where movement of the first follower610 along the working surface of the cam 620 changes a z-axis positionof the first extruder. For example, the working surface of the cam 620may be movable relative to the first extruder along the x-axis or they-axis. In addition to the first extruder, a second extruder may besupported on the carriage 650, where the second extruder defines asecond extrusion path different than the first extrusion path of thefirst extruder.

In certain implementations, such as the embodiment of FIGS. 6 and 7, thecarriage 650 may include or otherwise be coupled to a cam 620, a firstfollower 610, and a second follower 612. Alternatively, one or more ofthese components may be included on one or more modular extruders thatare configured for coupling to or within the carriage 650. Regardless,one or both of a sub-carriage and an extruder may be structurallyconfigured to move with one or more of the first follower 610 and thesecond follower 612. Thus, one or more of the first follower 610 and thesecond follower 612 may be positionally (but not rotationally) fixedrelative to the carriage 650 and/or an extruder coupled thereto.

The carriage 650 (or a portion thereof, such as one or more of the firstsub-carriage 651 and the second sub-carriage 652) may be pivotallyconnected to, or pivotally-disposed relative to, the gantry 660. Thus,when the carriage 650, an extruder, or a sub-carriage is lifted (e.g.,via the first follower 610 through movement thereof along the workingsurface of the cam 620), that component may pivot or otherwise move uprelative to the gantry 660.

The gantry 660 may generally include a structure upon which the extruderassembly 600 resides within a three-dimensional printer. For example,the gantry 660 may be connected to, or be in communication with, anx-y-z positioning assembly for positioning the extruder assembly 600within a build volume of a three-dimensional printer. In general, thegantry 660 may include a guide surface 662 upon which the extruderassembly 600 can move along one or more of the x-axis and the y-axis.For example, the extruder assembly 600 may include a gantry 660 and acarriage 650 as described herein, where the gantry 660 has a guidesurface 662 defining an axis perpendicular to the z-axis, a firstextruder is supported on the carriage 650 (e.g., in the firstsub-carriage 651), and the carriage 650 is movable along the guidesurface 662 of the gantry 660 in at least one direction along the axisthat is perpendicular to the z-axis (e.g., an x-axis or a y-axis). Inthis manner, and as shown in FIGS. 6 and 7, at least one of the damper680 or the support 670 may be disposed in a fixed location along theaxis that is perpendicular to the z-axis.

The gantry 660 may further include, or otherwise be engaged with, thesupport 670. Thus, the support 670 may reside on the gantry 660—forexample, the support 670 may be fixed on the gantry 660 and engageablewith the extruder assembly 600 via movement of the extruder assemblyalong an axis that intersects the z-axis (e.g., an x-axis or a y-axis).The support 670 may also or instead be coupled to a side of athree-dimensional printer or another component of the three-dimensionalprinter. Regardless, the support 670 may be engageable with an end ofthe cam 620 to move the cam 620 (e.g., translate, toggle, or slide thecam 620) relative to the carriage 650.

As described above, the cam 620 may have a working surface movablerelative to at least one of the extruders of the extruder assembly 600and shaped to translate a first movement of the cam 620 along an x-axisor a y-axis into a second movement of the first follower 610 along thez-axis. In this manner, the first follower 610 may be movable along theworking surface of the cam 620 as the working surface moves relative toone or more of the first extruder and the first sub-carriage 651 toraise the first follower 610 along the z-axis. The support 670 may beengageable with the cam 620 to reverse the first movement of the cam 620and lower the working surface adjacent to the first follower 610 alongthe z-axis. Thus, the working surface of the cam 620 may be movablerelative to one or more of the first extruder and the first sub-carriage651 in response to a force associated with engagement of the support 670with the cam 620.

The damper 680 may be coupled to the support 670. The damper 680 may beengageable with one or more of the first extruder and the firstsub-carriage 651 to receive a z-axis load therefrom and to decouple thefirst follower 610 from the working surface of the cam 620 as thesupport 670 lowers the working surface of the cam 620 adjacent to thefirst follower 610. More specifically, the damper 680 may engage withthe second follower 612.

In certain implementations, the damper 680 may include an arm that iscantilevered from the support 670 along one or more of the x-axis ory-axis. In this manner, the support 670, the damper 680, and the cam 620may work together to adjust a z-axis position of an extruder in thecarriage 650 on the gantry 660. For example, the cam 620 may be a linearcam, where the working surface of the cam 620 has a firsttwo-dimensional profile in a plane defined by the z-axis and anintersecting (e.g., perpendicular) axis such as the y-axis. The arm ofthe damper 680 may have a second two-dimensional profile in the planedefined by the z-axis and the y-axis, where the arm of the damper 680 isengageable with the second follower 612 to move the second follower 612along the second two-dimensional profile of the arm as the z-axis loadof an extruder is supported on the arm. As demonstrated in FIGS. 6 and7, the first two-dimensional profile of the working surface of the cam620 may be different from the second two-dimensional profile of the armof the damper 680. However, although different, these dimensionalprofiles may be sized and shape to work in conjunction with one anotherto mitigate noise or vibration when adjusting the z-axis position of anextruder in the extruder assembly 600. For example, the contact surface682 of the damper 680 may include an incline to gradually lower thesecond follower 612 as the carriage moves away from the support 670.

As described herein, the second follower 612 may be disposed on orwithin one or more of the first extruder and the first sub-carriage 651.As best shown in FIG. 7, the second follower 612 may be movable alongthe damper 680, where the z-axis load from one or more of the firstextruder and the first sub-carriage 651 is receivable by the damper 680via the second follower 612. To this end, the damper 680 may include acontact surface 682 for the second follower 612, where the contactsurface 682 is shaped to smoothly lower one or more of the firstextruder and the first sub-carriage 651 into a working position alongthe z-axis as the extruder assembly 600 moves away from the support 670along either the x-axis or the y-axis, depending upon the configurationof the gantry 660.

As discussed above, the first follower 610 and the second follower 612may be disposed on the carriage 650 and/or an extruder of the extruderassembly 600, where z-axis movement of one or more of the first follower610 and the second follower 612 may similarly provide z-axis movement tothe carriage 650 (or a portion thereof such as a sub-carriage) and/or anextruder of the extruder assembly 600. In general, the first follower610 may be movable along the working surface of the cam 620 (e.g., inrolling contact with the working surface of the cam 620), and the secondfollower 612 may be movable along the damper 680 (e.g., in rollingcontact with the damper 680 or support 670). To this end, the firstfollower 610 and the second follower 612 may be spaced apart from oneanother at least along the z-axis. The first follower 610 and the secondfollower 612 may also or instead be spaced apart from one another alongone or more of the x-axis and the y-axis.

Thus, generally as shown in FIGS. 6 and 7, the support 670 may have afirst surface 671 (e.g., a side surface) that contacts the cam 620 tomove the cam 620 in a first direction 601 along the y-axis (or thex-axis) as the carriage 650 approaches the support 670 along a seconddirection 602. The support 670 may further include, or otherwise work inconjunction with, a damper 680 having a contact surface 682 thatreceives a z-axis load of an extruder (or the sub-carriage configuredfor engagement with the extruder) as the carriage 650 approaches thesupport 670 by traveling in the second direction 602.

As further shown in FIG. 7, engagement of the first surface 671 of thesupport 670 with the cam 620 to cause movement of the working surface ofthe cam 620 in the first direction 601 may eventually fully disengagethe first follower 610 from the working surface of the cam 620. In thismanner, without the presence of the damper 680 in such an embodiment,the first extruder would drop down relatively abruptly, which couldcause unwanted noise or vibration. However, the damper 680 may receive az-axis load from the first extruder through engagement with the secondfollower 612. In this manner, as the carriage 650 continues to move awayfrom the support 670 in the first direction 601, the first extruder canbe gradually lowered, particularly where the contact surface 682 of thedamper 680 includes a sloped or inclined surface to provide a gradualz-axis position change for the second follower 612 (and thus an extruderor sub-carriage engaged thereto).

FIG. 8 shows a detail of a support engaged with a follower.Specifically, this figure shows a detail of a support 870 (which may bethe same as or similar to the supports 670 shown and described abovewith reference to FIGS. 6 and 7) engaged with a second follower movingdownward in the direction of the arrow 801 from a first position 812 ato a second position 812 b. More particularly, the support 670 mayinclude a damper 880 having a contact surface 882 that is sized andshaped (e.g., includes a two-dimensional profile in a plane thatintersects a z-axis, such as a plane defined by an x-axis and a y-axis)to gradually change the z-axis position of the second follower from thefirst position 812 a to the second position 812 b, and to then fullyrelease the second follower as the second follower moves beyond thevertical support limit of the damper 880. To this end, thetwo-dimensional profile of the contact surface 882 may include one ormore sloped portions. In particular, an inclined surface of the contactsurface 882 may include a first surface 884 angled or sloped to receivea load from an extruder as a plurality of extruders move toward thesupport 870 and a second surface 886 angled or sloped to smoothly andcontinuously lower the extruder into a working position as the pluralityof extruders move away from the support 870. In this manner, the secondfollower can be released from contact with the contact surface 882 ofthe damper 880 in a relatively gradual manner, which can aid inmitigating noise or vibration of the associated change in z-axisposition for an extruder or a sub-carriage that is coupled to the secondfollower.

FIG. 9 shows a side view of an extruder in an ‘up’ position, and FIG. 10shows a side view of an extruder in a ‘down’ position. These figuresdemonstrate how the extruder 900 (or a carriage or sub-carriage to whichthe extruder is coupled) may be pivotable to change a z-axis positionthereof. As shown in FIG. 9, a gap 902 may be present between anextruder portion 904 and a structure 906, e.g., when the extruder 900(and therefore the extruder portion 904) is lifted into an inactiveposition using the techniques described herein. Also, as shown in FIG.10, the extruder 900 in the active or down position may contact theother structure 906, which may be a carriage, a sub-carriage, frame, oranother component. This contact, if initiated in a relatively abrupt andsudden manner, may cause undesired noise and/or vibration in athree-dimensional printer. This may be further amplified if thecomponents that come in contact from a downward movement of an extruderare each made from a metal or a similar material. Thus, dampingtechniques as described herein may be advantageous to mitigate suchundesired noise or vibration.

Therefore, as described herein, a three-dimensional printer may includea build plate having a substantially planar surface and a plurality ofextruders, where each of the plurality of extruders defines a respectiveextrusion orifice directed toward the build plate, and where eachextrusion orifice is supported above the build plate at a respectiveheight along a z-axis perpendicular to the substantially planar surfaceof the build plate. The three-dimensional printer may further include acam having a working surface engageable with a first extruder of theplurality of extruders, where the working surface of the cam is moveablerelative to the first extruder to change a z-axis position of the firstextruder relative to at least one other one of the plurality ofextruders. The three-dimensional printer may also or instead include asupport engageable with the cam to move the cam in a manner that lowersthe working surface supporting the first extruder, and a damper coupledto the support. The damper may be engageable with the first extruder toreceive a z-axis load from the extruder thereby decoupling the firstextruder from the cam as the contact with the support lowers the workingsurface.

The plurality of extruders and the cam may be movable together in afirst direction parallel to the substantially planar surface of thebuild plate (e.g., along one or more of the x-axis and the y-axis).Further, the support may be selectively engageable with the cam to movethe cam relative to the plurality of extruders in a second directionthat is opposite the first direction, where a movement of the camrelative to the first extruder in the second direction decouples thefirst extruder from the cam.

As discussed above, the damper may include an arm cantilevered from thesupport in a direction parallel to the substantially planar surface ofthe build plate. The arm may include an inclined surface extendingobliquely to the substantially planar surface of the build plate. Thisinclined surface may be positioned to make an initial contact with thefirst extruder as the damper engages the first extruder, where thez-axis load of the first extruder is received by the arm as the firstextruder moves toward the support and away from the build plate alongthe inclined surface. The inclined surface may include a first surfaceangled to receive a load from the first extruder as the plurality ofextruders move toward the support and a second surface angled tosmoothly and continuously lower the first extruder into a workingposition as the plurality of extruders move away from the support.

FIG. 11 is a flowchart of a method for changing a z-axis position of anextruder in an extruder assembly featuring a plurality of extruders. Themethod 1100 may utilize any of the extruder assemblies,three-dimensional printers, or other systems and components describedherein. In general, the method 1100 may be used for extruder heighttoggling in a three-dimensional printer having a multi-extruderassembly.

As shown in step 1102, the method 1100 may include moving a plurality ofextruders within a plane parallel to a substantially planar surface of abuild plate, e.g., along an x-y plane. Each of the plurality ofextruders may define a respective extrusion orifice supported above thebuild plate at a respective height above the substantially planarsurface of the build plate. For example, the plurality of extruders mayinclude a first extruder disposed at a printing height, a secondextruder disposed at a non-printing height, with a cam coupled to (orotherwise in direct or indirect mechanical engagement with) theextruders for changing the z-axis height of one or more of theextruders.

To facilitate changing the z-axis height of an extruder, one or more ofthe plurality of extruders may be movable relative to a gantry along az-axis. For example, one or more of the plurality of extruders (or asub-carriage or the like that holds one or more of the plurality ofextruders) may be pivotally engaged (e.g., through a hinged connectionor the like) to the gantry or a component coupled to the gantry (e.g., acarriage or a portion thereof). In this manner, a z-axis position of anextrusion orifice of an extruder may be movable via a pivoting motion ofthe extruder. Thus, a force applied to an extruder (or a componentengaged with the extruder, such as a follower) may provide such apivoting motion to move the z-axis position of the extrusion orifice ofthe extruder. This may be used to toggle the extruder between a printingheight and a non-printing height within a build volume of athree-dimensional printer.

As shown in step 1104, the method 1100 may include moving a workingsurface of a cam relative to a first extruder of the plurality ofextruders. Movement of the working surface may change a z-axis positionof the first extruder relative to the build plate. More particularly,the working surface of the cam may engage with a first follower that ismovable along the working surface, following a contoured pathcorresponding to a two-dimensional profile of the working surface of thecam. This two dimensional profile of the working surface of the cam mayinclude one or more of peaks, valleys, plateaus, ramped surfaces, and soon corresponding to different z-axis heights relative to thesubstantially planar surface of the build plate. Thus, moving theworking surface of the cam may cause the follower to traverse along thecontoured path corresponding to the two-dimensional profile, thuschanging the z-axis height of the follower. The follower may beconfigured to freely rotate relative to the first extruder, but mayotherwise be in a fixed position relative to the first extruder. Thus,when the follower changes z-axis height because of movement thereofalong the working surface, the first extruder may similarly change itsz-axis height. In this manner, toggling or other movement of the workingsurface may cause a change in z-axis height for the first extruder.

As shown in step 1106, the method 1100 may include engaging a supportwith the cam to provide movement of the working surface. That is, theplurality of extruders and the cam may move together in a firstdirection, and engaging the support with the cam may move the cam in asecond direction, opposite the first direction, to provide movement ofthe working surface of the cam.

In this manner, the method 1100 may include moving the cam from a firstposition to a second position relative to the plurality of extruders forchanging the z-axis height of one or more of the extruders. Moving thecam between these positions may be accomplished by moving the pluralityof extruders such that the cam contacts a portion of thethree-dimensional printer, e.g., a portion external to the plurality ofextruders or the carriage, such as the support. Thus, the method 1100may generally include moving, through movement of the cam, an extruderof a multi-extruder assembly. For example, this may include one or moreof: (i) moving, through movement of the cam, a first extruder from theprinting height to the non-printing height; and/or (ii) moving, throughmovement of the cam, a second extruder from the non-printing height tothe printing height.

As shown in step 1108, the method 1100 may include engaging a damperwith the first extruder to receive a z-axis load from the firstextruder. More particularly, an extruder assembly may include a secondfollower that is movable along a contact surface (e.g., a top surface)of the damper. Similar to the first follower, the second follower may beconfigured to freely rotate relative to the first extruder, but mayotherwise be in a fixed position relative to the first extruder. Thus,when the second follower changes z-axis height because of movementthereof along the working surface, the first extruder may similarlychange its z-axis height. In this manner, if the contact surfaceincludes features to gradually change the z-axis position of the secondfollower (e.g., from a greater z-axis height to a lower z-axis heightrelative to the build plate), the first extruder may similarly changeits z-axis position in a relatively gradual manner. This may mitigatenoise or vibration caused by lowering the z-axis height of an extruder.

Thus, in general, the present teachings may include one or morefollowers and a cam that work together to move an extruder of amulti-extruder assembly along a z-axis. In some instances, a follower isin a fixed position relative to the extruder and the cam moves thefollower thereby moving the extruder. However, it will be understoodthat, also or instead, the working surface may be in a fixed positionrelative to the extruder and a follower (e.g., on a cam) may move theworking surface thereby moving the extruder, for example as explained inmore detail with reference to FIGS. 12 and 13 described below.

FIG. 12 shows an extruder assembly with a first extruder in a ‘down’position, and FIG. 13 shows an extruder assembly with a first extruderin an ‘up’ position. The extruder assembly 1200 may be similar to thosedescribed elsewhere herein, but in this exemplary embodiment of anextruder assembly 1200, the working surface 1222 may be fixed on one ormore extruders, where the cam 1220 includes a follower that moves alongthe fixed working surface 1222 of the extruder to change a z-axisposition of the extruder. The extruder assembly 1200 may thus generallyinclude a first extruder 1201, a second extruder 1202, and a cam 1220structurally configured to mechanically control a z-axis position of oneor more of the first extruder 1201 and the second extruder 1202.

The first extruder 1201 may define a first extrusion path 1206, where atleast one portion of the first extrusion path defines a z-axis 1205. Asdiscussed above, the first extruder 1201 may include a working surface1222 shaped to translate a horizontal movement (e.g., in one or more ofthe first direction 1232 and the second direction 1234) along theworking surface 122 into a vertical movement of the first extruder 1201along the z-axis 1205.

The cam 1220 may have a first follower 1210 that is horizontally movablerelative to the first extruder 1201 and positioned to travel along theworking surface 1222. The first follower 1210 may be the same as orsimilar to any of the followers described herein, e.g., including abearing, a rotating wheel, or the like. In general the first follower1210 may be disposed in a fixed location on the cam 1220, i.e., suchthat horizontal movement of the cam 1220 causes a similar horizontalmovement for the first follower 1210, e.g., along the working surface1222. That is, the first follower 1210 may be movable along the workingsurface 1222 of the of the first extruder 1201 as the first follower1210 moves in a first direction 1232 relative to the first extruder 1201to lower the working surface 1222 along the z-axis 1205.

It will be understood that the exemplary embodiment of the extruderassembly 1200 shown in FIGS. 12 and 13 may further include one or moreof a support and a damper as shown and described elsewhere herein. Thatis, the extruder assembly 1200 may include a support (not shown in FIGS.12 and 13) engageable with the cam 1220 to move the cam 1220 in a seconddirection 1234 opposing the first direction 1232 to raise the workingsurface 1222 along the z-axis 1205. The support may also or instead beengageable with the cam 1220 to move the cam 1220 in the first direction1232 to lower the working surface 1222 along the z-axis 1205. Further,the extruder assembly 1200 may include a damper (not shown in FIGS. 12and 13), which may or may not be coupled to the support. The damper maybe engageable with the first extruder 1201 to receive a z-axis load fromthe first extruder 1201 and to decouple the first follower 1210 from theworking surface 1222 as the support lowers the working surface 1222beneath first follower 1210 in response to a movement in the firstdirection 1234.

In general, and as described above, the cam may be a “basher bar” or a“toggle bar” on the carriage that moves horizontally to toggle thevertical height of one of the extruders of a multi-extruder assembly,e.g., from an inactive position (with a nozzle position disposed above aprinting plane along the z-axis) to an active position (with a nozzleposition disposed at or below a printing plane along the z-axis).Furthermore, this toggle bar may extend vertically from both sides ofthe multi-extruder assembly so that the height adjustment can beinitiated by contacting a side of the multi-extruder to any surroundingstructure, e.g., the frame of a printer, or the support, damper, orother features described herein. It will be appreciated that thisconfiguration facilitates passive, mechanical control of extruder heightwherein the extruder is raised and lowered by contacting opposing sidesof the multi-extruder assembly, e.g., by moving the multi-extruderassembly in the x-y plane of a build volume to contact a surroundingframe or other surrounding structures and move the toggle bar back andforth. In this manner, extruder height can advantageously be adjustedwithout the need for additional active components such as motors,electronic actuators, or the like.

Thus, in one aspect, an extruder assembly includes one or moreextruders—e.g., a first extruder and a second extruder movably coupledto the first extruder to permit vertical movement of the second extruderrelative to the first extruder, or vice-versa. The extruder assembly mayfurther include a coupler structurally configured to mechanicallycontrol a z-axis position of one extruder relative to another extruderin the extruder assembly (e.g., the second extruder relative to thefirst extruder). The coupler may include one or more of the componentsdescribed herein for moving the z-axis position of an extruder, such asa cam and one or more followers. For example, the coupler may include ahorizontal slider structurally configured to cause upward movement ofthe second extruder in response to a first horizontal movement in afirst direction and to permit downward movement of the second extruderin response to a second horizontal movement in a second directionopposing the first direction. The coupler may extend horizontally fromthe extruder assembly to expose a first end and a second end thatprovide control surfaces to move the coupler horizontally in the firstdirection and the second direction respectively.

The extruder assembly featuring such a coupler may further include asupport in a predetermined position within a three-dimensional printer.The support may include a first surface and a second surface, where thefirst surface is shaped to receive and vertically support the secondextruder as the extruder assembly horizontally contacts the support, andwhere the second surface is shaped to concurrently move the coupler inthe second direction as the extruder assembly horizontally contacts thesupport. The coupler or the second extruder may include a workingsurface with a ramp shaped to gradually raise and lower the secondextruder between an active position with an exit orifice below a lowestpoint of the first extruder and an inactive position with the exitorifice above the lowest point of the first extruder. Further, theworking surface may include a plateau above the ramp to support thesecond extruder in the inactive position and a ridge. The ridge may havea height greater than the plateau and the ridge may be positionedbetween the plateau and the ramp to bi-stably retain the second extruderin the inactive position when the extruder assembly is not engaged withthe damper.

Movement of an extruder in a multi-extruder assembly along the z-axismay be assisted by, or facilitated by, a biasing member, e.g., aflexible steel spring. For example, in certain implementations, anextruder in a multi-extruder assembly is biased toward an at-restposition, and movement of a cam as described herein may act against thisbiasing force to move the extruder from the at-rest position to anotherposition (e.g., a printing position).

The extruder or the carriage may include a hinged connection, wherez-axis motion is facilitated by the hinge, e.g., such that one or moreof the extruders (e.g., both of the extruders) pivots about an axisthrough the hinge. This pivoting motion may also or instead serve toengage and disengage an extruder from a single, common filament drivewheel, so that an inactive extruder is disengaged from contact with thedrive wheel when in a raised, pivot position.

Further, a dual carriage assembly that includes mechanical toggling ofone or multiple extruders or extruder components may lead to audiblenoise during operation. The present teachings, however, may be used tosignificantly reduce noise levels during operation without the need foradditional electromechanical architecture.

The toggle for multiple extruders as described herein may include one ormore of the following: (i) mechanical actuation to perform an upwardtoggle, where a follower rides along a working surface of a cam to pushone side of a carriage from a down position to an up position; (ii)mechanical actuation used to perform a downward toggle, where a followerrides along the working surface of the cam and slides from the upposition to the down position (e.g., this may be the opposite of theupward toggle); (iii) mechanical damping for noise and vibrationproduced from toggling, e.g., from the follower sliding down the workingsurface of the cam.

Thus, in an aspect, a three-dimensional printer includes a firstextruder and a second extruder movable independently from the firstextruder in a z-direction within a build volume of the three-dimensionalprinter, the second extruder including a first bearing and a secondbearing. The three-dimensional printer may also include a toggle barslidably coupled to the second extruder, the toggle bar including aninclined surface positioned to raise the second extruder in thez-direction in response to a movement of the toggle bar in a firstdirection. The three-dimensional printer may further include a supportarm having a second inclined surface to receive a load of the secondextruder from the toggle bar as the second extruder approaches thesupport arm, the support arm further including a toggling surface tomove the toggle bar in a second direction as the second extruderapproaches the support arm, thereby displacing the toggle bar andpermitting the second extruder to be lowered in the z-direction alongthe second inclined surface as the second extruder subsequently movesaway from the support arm.

The above systems, devices, methods, processes, and the like may berealized in hardware, software, or any combination of these suitable fora particular application. The hardware may include a general-purposecomputer and/or dedicated computing device. This includes realization inone or more microprocessors, microcontrollers, embeddedmicrocontrollers, programmable digital signal processors or otherprogrammable devices or processing circuitry, along with internal and/orexternal memory. This may also, or instead, include one or moreapplication specific integrated circuits, programmable gate arrays,programmable array logic components, or any other device or devices thatmay be configured to process electronic signals. It will further beappreciated that a realization of the processes or devices describedabove may include computer-executable code created using a structuredprogramming language such as C, an object oriented programming languagesuch as C++, or any other high-level or low-level programming language(including assembly languages, hardware description languages, anddatabase programming languages and technologies) that may be stored,compiled or interpreted to run on one of the above devices, as well asheterogeneous combinations of processors, processor architectures, orcombinations of different hardware and software. In another aspect, themethods may be embodied in systems that perform the steps thereof, andmay be distributed across devices in a number of ways. At the same time,processing may be distributed across devices such as the various systemsdescribed above, or all of the functionality may be integrated into adedicated, standalone device or other hardware. In another aspect, meansfor performing the steps associated with the processes described abovemay include any of the hardware and/or software described above. Allsuch permutations and combinations are intended to fall within the scopeof the present disclosure.

Embodiments disclosed herein may include computer program productscomprising computer-executable code or computer-usable code that, whenexecuting on one or more computing devices, performs any and/or all ofthe steps thereof. The code may be stored in a non-transitory fashion ina computer memory, which may be a memory from which the program executes(such as random-access memory associated with a processor), or a storagedevice such as a disk drive, flash memory or any other optical,electromagnetic, magnetic, infrared or other device or combination ofdevices. In another aspect, any of the systems and methods describedabove may be embodied in any suitable transmission or propagation mediumcarrying computer-executable code and/or any inputs or outputs fromsame.

The method steps of the implementations described herein are intended toinclude any suitable method of causing such method steps to beperformed, consistent with the patentability of the following claims,unless a different meaning is expressly provided or otherwise clear fromthe context. So, for example, performing the step of X includes anysuitable method for causing another party such as a remote user, aremote processing resource (e.g., a server or cloud computer) or amachine to perform the step of X. Similarly, performing steps X, Y and Zmay include any method of directing or controlling any combination ofsuch other individuals or resources to perform steps X, Y and Z toobtain the benefit of such steps. Thus, method steps of theimplementations described herein are intended to include any suitablemethod of causing one or more other parties or entities to perform thesteps, consistent with the patentability of the following claims, unlessa different meaning is expressly provided or otherwise clear from thecontext. Such parties or entities need not be under the direction orcontrol of any other party or entity, and need not be located within aparticular jurisdiction.

It will be appreciated that the methods and systems described above areset forth by way of example and not of limitation. Numerous variations,additions, omissions, and other modifications will be apparent to one ofordinary skill in the art. In addition, the order or presentation ofmethod steps in the description and drawings above is not intended torequire this order of performing the recited steps unless a particularorder is expressly required or otherwise clear from the context. Thus,while particular embodiments have been shown and described, it will beapparent to those skilled in the art that various changes andmodifications in form and details may be made therein without departingfrom the spirit and scope of this disclosure and are intended to form apart of the invention as defined by the following claims, which are tobe interpreted in the broadest sense allowable by law.

What is claimed is:
 1. A three-dimensional printer, comprising: a buildplate having a substantially planar surface; a plurality of extruders,each of the plurality of extruders defining a respective extrusionorifice directed toward the build plate, and each extrusion orificesupported above the build plate at a respective height along a z-axisperpendicular to the substantially planar surface; a cam having aworking surface engageable with a first extruder of the plurality ofextruders, the working surface of the cam moveable relative to the firstextruder to change a z-axis position of the first extruder relative toat least one other one of the plurality of extruders; a supportengageable with the cam to move the cam in a manner that lowers theworking surface supporting the first extruder; and a damper coupled tothe support, the damper engageable with the first extruder to receive az-axis load from the extruder thereby decoupling the first extruder fromthe cam as the contact with the support lowers the working surface. 2.The three-dimensional printer of claim 1, wherein the plurality ofextruders and the cam are movable together in a first direction parallelto the substantially planar surface of the build plate, the support isselectively engageable with the cam to move the cam relative to theplurality of extruders in a second direction, opposite the firstdirection, and a movement of the cam relative to the first extruder inthe second direction decouples the first extruder from the cam.
 3. Thethree-dimensional printer of claim 1, wherein the damper includes an armcantilevered from the support in a direction parallel to thesubstantially planar surface of the build plate.
 4. Thethree-dimensional printer of claim 3, wherein the arm includes aninclined surface extending obliquely to the substantially planarsurface, the inclined surface positioned to make an initial contact withthe first extruder as the damper engages the first extruder, and whereinthe z-axis load of the first extruder is received by the arm as thefirst extruder moves toward the support and away from the build platealong the inclined surface.
 5. The three-dimensional printer of claim 4,wherein the inclined surface includes a first surface angled to receivea load from the first extruder as the plurality of extruders move towardthe support and a second surface angled to smoothly and continuouslylower the first extruder into a working position as the plurality ofextruders move away from the support.
 6. The three-dimensional printerof claim 1, wherein the first extruder includes a first followerengageable with the working surface of the cam and movable along theworking surface of the cam as the working surface moves relative to thefirst extruder to raise the first follower along the z-axis.
 7. Thethree-dimensional printer of claim 6, wherein the first follower whereinthe damper is engageable with the first extruder to decouple the firstfollower from the working surface of the cam as the support lowers theworking surface of the cam adjacent to the first follower.
 8. Thethree-dimensional printer of claim 6, wherein the first extruderincludes a second follower movable along the damper, and wherein thez-axis load from the first extruder is receivable by the damper via thesecond follower.
 9. The three-dimensional printer of claim 8, whereinthe damper includes a contact surface for the second follower, thecontact surface shaped to smoothly lower the first extruder into aworking position along the z-axis as the first extruder moves away fromthe support along an x-axis or y-axis.
 10. The three-dimensional printerof claim 8, wherein the first follower is movable along the workingsurface of the cam in rolling contact with the working surface of thecam, and the second follower is movable along the damper in rollingcontact with the support.
 11. The three-dimensional printer of claim 8,wherein the first follower and the second follower are spaced apart fromone another at least along the z-axis.
 12. The three-dimensional printerof claim 1, further comprising a gantry and a carriage, wherein thegantry has a guide surface defining an axis perpendicular to the z-axis,the plurality of extruders are supported on the carriage, and thecarriage is movable along the guide surface of the gantry in at leastone direction along the axis perpendicular to the z-axis.
 13. Thethree-dimensional printer of claim 12, wherein at least one of thedamper or the support is in a fixed location along the axisperpendicular to the z-axis.
 14. The three-dimensional printer of claim12, wherein the working surface of the cam is movable relative to thefirst extruder along the axis perpendicular to the z-axis.
 15. Thethree-dimensional printer of claim 12, wherein the damper includes anarm cantilevered from the support along the axis perpendicular to thez-axis.
 16. The three-dimensional printer of claim 15, wherein the camis a linear cam, and the working surface of the cam has a firsttwo-dimensional profile in a plane defined by the z-axis and the axisperpendicular to the z-axis.
 17. The three-dimensional printer of claim16, wherein the arm has a second two-dimensional profile in the planedefined by the z-axis and the axis perpendicular to the z-axis, thefirst extruder includes a second follower, and the arm is engageablewith the second follower to move the second follower along the secondtwo-dimensional profile of the arm as the z-axis load of the firstextruder is supported on the arm.
 18. The three-dimensional printer ofclaim 17, wherein the first two-dimensional profile of the workingsurface of the cam is different from the second two-dimensional profileof the arm.
 19. A method comprising: moving a plurality of extruderswithin a plane parallel to a substantially planar surface of a buildplate, each of the plurality of extruders defining a respectiveextrusion orifice supported above the build plate at a respective heightabove the substantially planar surface; moving a working surface of acam relative to a first extruder of the plurality of extruders, movementof the working surface changing a z-axis position of the first extruderrelative to the build plate; and engaging a damper with the firstextruder to receive a z-axis load from the first extruder.
 20. Themethod of claim 19, wherein the plurality of extruders and the cam movetogether in a first direction, the method further comprising engaging asupport with the cam to move the cam in a second direction, opposite thefirst direction, to provide movement of the working surface.